A percutaneous transluminal angioplasty (PTA) of blood vessels including the coronary arteries (PTCA) is a very popular method to eliminate vessel narrowing or stenosis that obstructs blood flow to human organs. The success rates of coronary angioplasty procedures is inversely related to the extent of the vascular disease, and the patients intolerance towards myocardial ischemia during temporary blood flow obstruction.
One of the principle limitations of a coronary angioplasty is the complete obstruction of blood flow during the inflation of the balloon. After a short period of balloon occlusion, patients experience ischemia due to the lack of flow of oxygenated blood to the myocardium. Myocardial ischemia is usually indicated by either angina pectoris or cardiac arrhythmias. In the past, several perfusion balloon catheters were developed to overcome the problem of blood flow obstruction during percutaneous coronary interventions. U.S. Pat. No. 4,944,745 (Sograd) discloses a perfusion balloon catheter that allows passive perfusion of blood through a catheter whose balloon is obstructing blood flow. U.S. Pat. No. 4,909,252 (Goldberger) discloses a perfusion balloon catheter with a central opening allowing blood flow passage when the balloon is fully inflated. U.S. Pat. No. 5,087,247 (Horn et al) discloses a balloon perfusion catheter with an elongated flexible perfusion shaft with multiple openings proximal and distal to the balloon to permit blood flow through an artery during balloon inflation. WO 9732626 (Cox et al) discloses an inflatable balloon envelope allowing blood passage during inflation of the device.
However, perfusion balloon catheters placed into small arteries such as the coronary circulation have the disadvantage of limited blood perfusion capacity inherent to relatively small blood flow rates in those arteries. In times of increasing rates of coronary stenting, perfusion balloon catheters have become obsolete. For instance, a prolongation of the balloon dilatation process to achieve better angioplasty results is not any more necessary. The dilemma of the perfusion balloon was characterized in a publication by Ferrari et al (Coron Art Dis 1997) who conclude their studies with the statement that in “high-risk patients dependent on adequate coronary perfusion, autoperfusion balloons are not able to provide sufficient distal coronary blood flow during balloon inflation”. Insufficient blood flow distal to an inflated balloon causes hypoxia and ischemia of end organs because the oxygenation of tissue previously supplied with blood is reduced. Angioplasty is of high risk in patients who require dilatation of the unprotected trunk of the left main coronary artery. Tan et al (Circulation 2001) concluded that although percutaneous balloon interventions are a generally accepted treatment modality for coronary artery disease, left main PTCA remains are high risk procedure for the patient.
Another limitation of a coronary angioplasty is restenosis. Restenosis after PTCA has been successfully inhibited by ionizing radiation therapy applied prior to or shortly after angioplasty. Vascular brachytherapy using radioactive sources has become a new treatment option to prevent restenosis. Radioactive stents disclosed in U.S. Pat. No. 5,059,166 (Fischell et al) or radioactive catheters disclosed in U.S. Pat. No. 5,199,939 (Dake et al) have been introduced to minimize or eliminate neointimal hyperplasia after angioplasty. However, logistic complexities of using radiation sources in coronary arteries and radiation safety issues have prompted researcher to improve the irradiation technology. U.S. Pat. No. 5,951,458 (Hastings et al) discloses a radiation catheter that releases oxidizing agents such a H2O2 to prevent restenosis after cardiovascular interventions. The method described by Hastings helps to reduce radiation doses or treatment times necessary for a radioactive treatment to prevent restenosis.
Oxygenated fluorocarbons emulsions have been used to treat hypoxic and ischemic disorders. Oxygen-transferable fluorocarbon emulsions become known as artifical blood substitutes more than twenty years ago. In U.S. Pat. No. 3,958,014 and U.S. Pat. No. 4,252,827, fluorocarbon emulsion are disclosed that have a small particle size of 0.02 to 0.25 microns, and are injectable into the blood stream. In U.S. Pat. No. 4,445,500, Osterholm teaches that oxygenated fluorocarbon emulsions can be injected into the cerebrospinal pathway to improve aerobic respiration of tissue. U.S. Pat. No. 4,795,423 (Osterholm) discloses an intraocular perfusion with perfluorinated substances to treat ischemic retinopathy.
The local delivery of drugs during an angioplasty procedure using fluids injected into organs via catheters for treatment purpose has been disclosed previously. U.S. Pat. No. 4,636,195 (Wolinsky) teaches that substances may be injected to the vessel wall through a porous balloon catheter. However, the injection of substances into the walls of blood vessels may cause damage of vascular structures during the injection process. The damage of the vessel wall during initial treatment may promote neointimal hyperplasia as a cause of stenosis. Even modified surfaces of infusions balloons with dimples as disclosed in U.S. Pat. No. 6,048,332 may not completely prevent vascular injury during injection therapeutic agents at the time of balloon inflation.